The present invention relates to a means of connecting a pusher boat and a barge.
Barges are widely employed for the transport of cargoes in rivers, canals and lakes, and even in open sea. There are two conventional methods to move the barges, one being to tow by a towboat and the other being to push by a pusher boat. The present invention relates to the latter case where the barge is connected with the pusher boat to form a pusher-barge combination system. More particularly, the invention relates to a means of connecting a pusher boat and a barge to form an improved pusher-barge combination system with excellent performance.
The methods of connecting a pusher boat and a barge are classified broadly into the following three categories:
(a) Rope-connection; PA1 (b) Articulate mechanical connection by a pair of transverse horizontal co-axial connecting pins to permit relative pitching of the pusher boat and the barge; and PA1 (c) Rigid mechanical connection permitting no relative motions of the pusher boat and the barge.
Though widely employed even now, the rope-connection under (a) above results in such a poor navigability in waves that any safe and steady services in wavy sea cannot be expected.
The articulate mechanical connection methods under (b) above are well-developed now, particularly by the aid of the connecting means invented by the present applicant and patented in the United States under U.S. Pat. No. 3,844,245 (corresponding U.K. Pat. No. 1,386,185 and German Federal Republic Pat. No. 2,303,818), U.S. Pat. No. 3,935,831 (corresponding Canadian Pat. No. 1,026,164, French Pat. No. 75/11118, German Federal Republic Pat. No. 2,516,372 and U.K. Pat. No. 1,465,207) and U.S. Pat. No. 4,805,548 (corresponding U.K. Pat. No. 2,108,436). These three inventions have been so successful that the performance of pusher-barge combinations systems has been remarkably improved up to the level assuring safe and steady navigations in the rough ocean areas.
In spite of such a good performance in regard to the navigability in rough sea, the articulate connection methods as per (b) above have two demerits, one being the wide clearance between two hulls for permitting free relative pitching which causes such heavy eddies that the running speed is lowered and the other being the lack of comfortableness to the crew on board the heavily pitching pusher boat swung by the barge.
These demerits can be overcome by the rigid connection methods under (c) above which do not permit any relative motion of two watercraft and, accordingly, permit reduction of the clearance between the hulls to a minimum to improve the propulsive performance and, at the same time, assure a superior seaworthiness and comfortableness in rough sea. The apparatus for connecting a pusher boat and a barge according to the present invention belongs to this category (c) above--rigid mechanical connection method.
In the earlier stage, rigid mechanical connection methods of several types were invented mainly in the United States. These methods proposed in earlier days have a common design principle that the stern of the barge is made in a special shape and the bow or the whole hull of the pusher boat is inserted into or land on this specially shaped stern portion of the barge. According to such designs, connection and disconnection can take place only when both the pusher boat and the barge are approximately in the fully loaded condition. Such connection systems have practically no self-adaptability to the change of draft of the barge due to loading and unloading and, further, if the draft of the barge changes widely due to collision and subsequent flooding, emergency disconnection of the pusher boat would become impossible.
As a rigid connection method permitting self-adaptation to the change of draft of the barge, the present applicant has an invention as per Japanese Patent Journal No. S51-40352 and there is another as per Japanese Utility Model Journal No. S52-38000 which is generally similar to the former. (These two are hereinafter referred to as the "former inventions"). The basic design principle of these is that the pusher boat is equipped with three connecting pins--one pin at the bow end and two pins on both sides of the pusher boat--which are extended out axially so that their outer ends may be inserted into holes, in the wall of the stern notch of the barge, functioning as pin-end supporting means on the barge, to form a rigid connection through supporting the pusher boat at three points. If the pin-end supporting means on the barge hull are arranged vertically in two or more steps, connection can take place in two or more draft relationships. Further, prompt disconnection can take place simply by retracting the connecting pins in such an emergency case as is mentioned above.
Though the above-mentioned former inventions can meet the minimum necessary conditions of rigid connection, they involve some difficulties and inconveniences particularly in the course of connection, because the pin-end receiving means are simple holes and, particularly when the pusher boat and the barge are oscillating due to waves, it is very difficult to insert pins into them. Further, even when these holes are provided in plurality, two or three holes can be arranged in practice because of their large dimensions and, if the draft relationship is such that the pins are at a level between two vertically arranged holes, the draft must be adjusted through adding a big quantity of water ballast. In addition, the pusher boat must be kept disconnected during loading and unloading. The present invention is proposed in order to solve these problems involved in the connecting means of the former inventions.